Method of mapping physical resource to logical resource in wireless communication system

ABSTRACT

A method of mapping a physical resource to a logical resource in a wireless communication system is described. The method includes dividing a physical frequency band into at least one frequency partition. Each frequency partition is divided into a localized region and a distributed region in a frequency domain. The method further includes mapping the at least one frequency partition into at least one logical resource unit. The localized region is directly mapped into the logical resource unit and the distributed region is mapped into the logical resource unit after rearranging subcarriers within the distributed region.

This application is a Continuation of U.S. application Ser. No.14/506,280 filed Oct. 3, 2014, which is a continuation of U.S.application Ser. No. 14/107,964 filed Dec. 16, 2013 (now issued as U.S.Pat. No. 9,204,427 issued Dec. 1, 2015), which is a continuation of U.S.application Ser. No. 12/679,253 filed Mar. 19, 2010 (now issued as U.S.Pat. No. 8,625,568 issued Jan. 7, 2014), which is a National Stage under35 U.S.C. 371 of International Application No. PCT/KR2008/005500 filedSep. 17, 2008, which claims priority of Korean Application No.10-2007-0096625 filed Sep. 21, 2007, all of which are herebyincorporated by reference in their entirety.

BACKGROUND

Field of the Disclosure

The present invention relates to wireless communications, and moreparticularly, to a method of mapping a physical resource to a logicalresource.

Discussion of the Related Art

A wireless communication system is widely used to provide various typesof communication services. For example, the wireless communicationsystem provides voice and/or data services. The wireless communicationsystem can use a frequency division duplex (FDD) scheme or a timedivision duplex (TDD) scheme. In the FDD scheme, uplink transmission anddownlink transmission are achieved at the same time point whileoccupying different frequency bands. In the TDD scheme, uplinktransmission and downlink transmission are achieved at different timepoints while occupying the same frequency band.

In order to effectively use limited radio resources in the wirelesscommunication system, there are proposed methods and utilization forfurther effective transmission and reception in time, space, andfrequency domains. Orthogonal frequency division multiplexing (OFDM)uses a plurality of orthogonal subcarriers. Further, the OFDM usesorthogonality between inverse fast Fourier transform (IFFT) and fastFourier transform (FFT). A transmitter transmits data by performing theIFFT. A receiver restores original data by performing the FFT on areceived signal. The transmitter uses the IFFT to combine the pluralityof subcarriers. The receiver uses the FFT to split the plurality ofsubcarriers. According to the OFDM, complexity of the receiver can bereduced in a frequency selective fading environment of a broadbandchannel, and spectral efficiency can be increased when selectivescheduling is performed in a frequency domain by using a channelcharacteristic which is different from one subcarrier to another.Orthogonal frequency division multiple access (OFDMA) is an OFDM-basedmultiple access scheme. According to the OFDMA, efficiency of radioresources can be increased by allocating different subcarriers tomultiple users.

The institute of electrical and electronics engineers (IEEE) 802.16standard group was established in 1999 for broadband wireless access(BWA) standardization. A WirelessMAN-OFDMA standard has recently beendefined to use the OFDMA. At present, a logical frame structure of anIEEE 802.16-2004 system uses the TDD scheme in which a downlink frameand an uplink frame are separated by a guard time.

Accordingly, there is a need for a method capable of transmitting databy using a frame having a shorter length than a frame structure of theTDD scheme in consideration of improvement of cell coverage,maximization of spectral efficiency, improvement of efficiency formobility support, improvement of latency, etc.

SUMMARY OF THE INVENTION

The present invention provides a method of mapping a physical resourceto a logical resource.

According to an aspect of the present invention, there is provided amethod of mapping a physical resource to a logical resource in awireless communication system is provided, the method including:dividing a physical frequency band into at least one frequencypartition, wherein each frequency partition is divided into a localizedregion and a distributed region in a frequency domain; and mapping theat least one frequency partition into at least one logical resourceunit, wherein the localized region is directly mapped into the logicalresource unit and the distributed region is mapped into the logicalresource unit after rearranging subcarriers within the distributedregion.

According to another aspect of the present invention, there is provideda transmitter including: a radio frequency (RF) unit transmitting an RFsignal; and a processor that is connected to the RF unit, divides aphysical frequency band into at least one frequency partition, and mapsthe at least one frequency partition into at least one logical resourceunit, wherein each frequency partition is divided into a localizedregion and a distributed region in a frequency domain, the localizedregion is directly mapped into the logical resource unit and thedistributed region is mapped into the logical resource unit afterrearranging subcarriers within the distributed region.

According to the present invention, a distributed subcarrier allocationscheme and a localized subcarrier allocation scheme are supported in asubframe to increase efficiency of frequency resources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows an example of a frame structure.

FIG. 3 shows an example of a frame including a plurality ofpermutations.

FIG. 4 shows an example of a frame generated in every frequency band bydividing a whole frequency band.

FIG. 5 shows a subframe structure according to an embodiment of thepresent invention.

FIG. 6 shows a logical frame for a physical frame of FIG. 5.

FIG. 7 shows a frame structure according to another embodiment of thepresent invention.

FIG. 8 shows a logical frame for a physical frame of FIG. 7.

FIG. 9 is a flowchart showing a method of mapping a physical resource toa logical resource according to an embodiment of the present invention.

FIG. 10 shows segmentation supporting frequency reuse according to anembodiment of the present invention.

FIG. 11 shows a resource allocation unit according to an embodiment ofthe present invention.

FIG. 12 shows a method of dividing a data region according to anembodiment of the present invention.

FIG. 13 shows a method of dividing a data region according to anotherembodiment of the present invention.

FIG. 14 shows a method of determining a start position of a data regionaccording to an embodiment of the present invention.

FIG. 15 is a block diagram showing constitutional elements of a userequipment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a wireless communication system. The wireless communicationsystem can be widely deployed to provide a variety of communicationservices, such as voices, packet data, etc.

Referring to FIG. 1, the wireless communication system includes a basestation (BS) 20 and at least one user equipment (UE) 10. The UE 10 maybe fixed or mobile, and may be referred to as another terminology, suchas a mobile station (MS), a user terminal (UT), a subscriber station(SS), a wireless device, etc. The BS 20 is generally a fixed stationthat communicates with the UE 10 and may be referred to as anotherterminology, such as a node-B, a base transceiver system (BTS), anaccess point, etc. There are one or more cells within the coverage ofthe BS 20.

Hereinafter, a downlink denotes a communication link from the BS 20 tothe UE 10, and an uplink denotes a communication link from the UE 10 tothe BS 20. In downlink, a transmitter may be a part of the BS 20, and areceiver may be a part of the UE 10. In uplink, the transmitter may be apart of the UE 10, and the receiver may be a part of the BS 20.

There is no restriction on multiple access schemes used in the wirelesscommunication system. Various multiple access schemes may be used suchas code division multiple access (CDMA), time division multiple access(TDMA), frequency division multiple access (FDMA), single-carrier FDMA(SC-FDMA), orthogonal frequency division multiple access (OFDMA), etc.

FIG. 2 shows an example of a frame structure. A frame is a data sequenceused according to a physical specification in a fixed time duration.This may be found in section 8.4.4.2 of “Part 16: Air Interface forFixed Broadband Wireless Access Systems” in the institute of electricaland electronics engineers (IEEE) standard 802.16-2004 (hereinafter,Document 1).

Referring to FIG. 2, the frame includes a downlink (DL) frame and anuplink (UL) frame. In a time division duplex (TDD) scheme, UL and DLtransmissions are achieved at different time points but share the samefrequency band. The DL frame is temporally prior to the UL frame. The DLframe sequentially includes a preamble, a frame control header (FCH), aDL-MAP, a UL-MAP, and a burst region. Guard times are provided toidentify the UL frame and the DL frame and are inserted to a middleportion (between the DL frame and the UL frame) and a last portion (nextto the UL frame) of the frame. A transmit/receive transition gap (TTG)is a gap between a downlink burst and a subsequent uplink burst. Areceive/transmit transition gap (RIG) is a gap between an uplink burstand a subsequent downlink burst.

A preamble is used between a BS and a UE for initial synchronization,cell search, and frequency-offset and channel estimation. An FCHincludes information on a length of a DL-MAP message and a coding schemeof the DL-MAP.

The DL-MAP is a region for transmitting the DL-MAP message. The DL-MAPmessage defines access to a DL channel. The DL-MAP message includes aconfiguration change count of a downlink channel descriptor (DCD) and aBS identifier (ID). The DCD describes a downlink burst profile appliedto a current MAP. The downlink burst profile indicates characteristicsof a DL physical channel. The DCD is periodically transmitted by the BSby using a DCD message.

The UL-MAP is a region for transmitting a UL-MAP message. The UL-MAPmessage defines access to a UL channel. The UL-MAP message includes aconfiguration change count of an uplink channel descriptor (UCD) andalso includes an effective start time of uplink allocation defined bythe UL-MAP. The UCD describes an uplink burst profile. The uplink burstprofile indicates characteristics of a UL physical channel and isperiodically transmitted by the BS by using a UCD message.

Hereinafter, a slot is a minimum unit of possible data allocation, andis defined with a time and a subchannel. The number of subchannelsdepends on a fast Fourier transform (FFT) size and time-frequencymapping. Each subchannel includes a plurality of subcarriers. The numberof subcarriers included in each subchannel differs according to apermutation rule. Permutation denotes mapping from a logical subchannelto a physical subcarrier. In full usage of subchannels (FUSC), eachsubchannel includes 48 subcarriers. In partial usage of subchannels(PUSC), each subchannel includes 24 or 16 subcarriers. A segment denotesat least one subchannel set.

In order for data to be mapped to physical subcarriers in a physicallayer, two steps are generally performed on the data. In a first step,the data is mapped to at least one data slot on at least one logicalsubchannel. In a second step, each logical subchannel is mapped to aphysical subcarrier. This is called permutation. Examples of thepermutation rule employed in the Document 1 above (i.e., the IEEE802.16-2004 standard) include FUSC, PUSC, optional-FUSC (O-FUSC),optional-PUSC (O-PUSC), adaptive modulation and coding (AMC), etc. A setof OFDM symbols using the same permutation rule is referred to as apermutation zone. One frame includes at least one permutation zone.

The FUSC and the O-FUSC are used only in downlink transmission. The FUSCconsists of one segment including all subchannel groups. Each subchannelis mapped to a physical subcarrier distributed over the entire physicalchannel. This mapping varies for each OFDM symbol. A slot consists ofone subchannel on one OFDM symbol. The O-FUSC uses a pilot allocationscheme different from that used in the FUSC.

The PUSC is used both in downlink transmission and uplink transmission.In downlink, each physical channel is divided into clusters, each ofwhich includes 14 contiguous subcarriers on two OFDM symbols. Thephysical channel is mapped to six groups. In each group, pilots areallocated in fixed positions to each cluster. In uplink, subcarriers aredivided into tiles, each of which includes four contiguous physicalsubcarriers on three OFDM symbols. The subchannel includes six tiles.Pilots are allocated to the corners of each tile. The O-PUSC is usedonly in uplink transmission. Each tile includes three contiguousphysical subcarriers on three OFDM symbols. Pilots are allocated to thecenter of each tile.

FIG. 3 shows an example of a frame including a plurality ofpermutations. The frame may be a physical frame.

Referring to FIG. 3, in a DL frame, a preamble, an FCH, and a DL-MAPmust appear in every frame. A PUSC permutation is applied to the FCH andthe DL-MAP. A PUSC permutation, an FUSC permutation, an optional FUSCpermutation, and an AMC permutation may appear in the DL frame. Thepermutations appeared in the DL frame can be specified in the DL-MAP. APUSC permutation, an optional PUSC, and an AMC permutation may appear ina UL frame. The permutations appeared in the UL frame can be specifiedin a UL-MAP.

Data or control information in frames can be accurately obtained byusing the preamble, the FCH, the DL-MAP, or the like included in eachframe.

A BS can use a part of frequency band by dividing the whole frequencyband. For example, neighboring BSs may use different frequency bands toavoid inter-BS interference. Alternatively, one BS may divide one cellinto a plurality of sectors so that different frequency bands are usedby the respective sectors. As such, frames can be transmitted for eachdivided frequency band.

FIG. 4 shows an example of a frame generated in every frequency band bydividing a whole frequency band. This is a case where frames having thesame format are generated and transmitted in respective frequency bands.

Referring to FIG. 4, the whole frequency band can be divided into aplurality of frequency bands so that frames can be generated andtransmitted in the respective frequency bands. In this case, therespective frequency bands may be used by different BSs. Alternatively,the respective frequency bands may be used by one BS in differencesectors. The respective frequency bands may be either contiguousfrequency bands or scattered frequency bands on the whole frequencyband. In each frequency band, a frame can be generated and transmittedusing one system. That is, data can be transmitted through a framehaving the same format in each frequency band.

The whole frequency band can be divided into a plurality of frequencybands so that frames with different formats are generated andtransmitted in the respective frequency bands. The frames can begenerated and transmitted using other systems in the respectivefrequency bands. When the frames are generated and transmitted usingother systems in an arbitrary frequency band, there is a need to processsignals repetitively or independently. As a result, there may be arestriction on the effective use of limited radio resources. Inparticular, a head portion of a control signal causes a significantoverhead since the head portion of the control signal is repeated ineach frame, thereby decreasing a data transfer amount of the system. Inaddition, when the frames of other systems are used, it is difficult toconfigure a channel having a structure flexible in various bandwidths.

Accordingly, when transmitting data, a frame length needs to be shorterthan that of a TDD-based frame. A frequency division duplex (FDD)structure may have a shorter frame length than the TDD structure. Forexample, when the TDD-based frame has a length of 5 msec, a frame (i.e.,region) for supporting FDD can have a length of 1 to 3 msec. Conditionsto be considered in the designing of a new frame are as follows.

(1) A distributed or localized subcarrier allocation scheme is supportedwithin a single frame.

(2) A subcarrier subchannel allocation scheme is easily used in astructure of the frame.

(3) Ranging or control signal transport channels using localized subbandallocation within an uplink frame is supported to provide an improvedcoverage.

(4) An overhead of MAP information on resources allocated to each UE isminimized.

(5) Unlike the conventional TDD-based control information transmissionscheme, hierarchical control information capable of supporting atransmission time interval (TTI) can be transmitted.

(6) A conventional system can be supported within a conventionalfrequency band.

(7) The conventional system co-exists with a new system in a singlefrequency band.

(8) Performance deterioration does not occur in a UE of the conventionalsystem coexisting with the new system.

(9) The new system can independently operate, and generation ofadditional control signals is minimized.

(10) A channel structure can be supported in a flexible manner within acontiguous or scattered frequency band.

(11) The control signal can be easily supported by a single-mode UEsupporting one system and a dual-mode UE supporting two or more systems.

The frame is designed to satisfy all or some of the aforementionedconditions.

FIG. 5 shows a subframe structure according to an embodiment of thepresent invention. The subframe is a downlink frame that can indicatefrequency-time physical resource allocation.

Referring to FIG. 5, a physical frame includes a control channel regionand/or a data region.

The control channel region may be a common control channel and/or adedicate control channel. The common control channel is used to transmitcontrol information that can be commonly utilized by UEs. The controlinformation may be system configuration information which is commonwithin a whole or part of a subframe, a frame, or a super-frame. Thesuper-frame may consist of one or more frames. The frame may consist ofone or more subframes. A three hierarchical frame configuration can beoptionally configured in one or more layers. The dedicated controlchannel is utilized to transmit control information required for aspecific UE. A BS can optionally utilize the dedicated control channelto transmit system configuration information or resource allocationinformation for a specific UE.

The data region includes a distributed region and/or a localized region.The distributed region and the localized region include a plurality ofsubcarriers in a frequency domain and include a plurality of OFDMsymbols in a time domain. The distributed region and the localizedregion can be distinguished in the frequency domain. That is, thedistributed region and the localized region use a frequency divisionmethod. The distributed region and the localized region may usedifferent permutation rules. In one slot (or one subframe) unit, thedistributed region and/or the localized region may occupy differentfrequency bands. A distributed subcarrier allocation scheme and/or alocalized subcarrier allocation scheme can be used within one slotconstituting the subframe. In the distributed subcarrier allocationscheme, a plurality of subcarriers constituting one piece of data aremapped in the data region in a distributed manner. In the localizedsubcarrier allocation scheme, a plurality of subcarriers constitutingone piece of data are mapped in a consecutive manner. Since thedistributed subcarrier allocation scheme and the localized subcarrierallocation scheme are supported in the frequency domain within one slotor one frame, efficiency of frequency resources can be increased.

A plurality of frames can constitute one super-frame. It is assumedherein that one super-frame includes 7 frames. However, this is forexemplary purposes only, and the number of frames included in thesuper-frame is not limited thereto. One frame can be transmitted in onetransmission time interval (TTI) which is a time for concurrentlytransmitting data. Alternatively, one subframe can be transmitted in oneTTI. 1^(st) to 7^(th) frames are transmitted in a temporal order. The BScan transmit the super-frame by including a preamble or a first commoncontrol channel (i.e., common control CH #1) in the 1^(st) frame of thesuper-frame. Further, the BS can transmit the super-frame by including asecond common control channel (i.e., common control CH #2) in the 4^(th)frame of the super-frame. The dedicated control channel can be includedin the remaining frames. The BS can report information on the 7 framesincluded in the super-frame by using the common control CH #1. The BScan report information on the remaining frames transmitted later byusing the common control CH #2.

As described above, the preamble is included only in the 1st frame ofthe super-frame, and control information on radio resources allocated tothe UE is not reported in every frame but reported through hierarchicalmapping by being included only in some frames. Accordingly, an overheadcaused by the control signal can be reduced. In addition, a multi-userdiversity gain and a frequency diversity gain can be effectivelyobtained by separating the data region according to the frequencydivision method during a short frame duration.

FIG. 6 shows a logical frame for the physical frame of FIG. 5. Thelogical frame may be a logical downlink frame.

Referring to FIG. 6, the logical frame can be generated by performinglogical mapping from the physical frame. The physical frame can begenerated by performing physical mapping from the logical frame. Thephysical frame and the logical frame correspond to each other. A BS anda UE may know in advance information on physical mapping and logicalmapping.

The logical frame can include a MAP, an FCH, and a logical subchannelregion. A control channel region of the physical frame is logical-mappedto the MAP and the FCH. The MAP and the FCH can be temporally prior tothe logical subchannel region. The logical subchannel region includes aplurality of subchannels. The subchannel is a logical resource unit forresource allocation. A distributed region of the physical frame ismapped to a distributed logical subchannel region. A localized region ofthe physical frame is mapped to a localized logical subchannel region.In the mapping from the distributed region to the distributed logicalsubchannel region, subcarriers are distributed according to a specificpermutation. Mapping from the localized region to the localized logicalsubchannel region can be directly performed without the use of thepermutation.

The logical frame can determine logical subchannel numbers in thefrequency domain. The logical subchannel number can be a subchannelindex to be informed to the UE. The logical subchannel number for thedistributed logical subchannel region and the logical subchannel numberfor the localized logical subchannel may be numbers which are numberedstarting from the same starting point or different starting points. Forexample, if it is assumed that N logical subchannels are present in thefrequency domain, the distributed logical subchannel number can be setto a number in the range of 1 to N belonging to the distributed logicalsubchannel region. The localized logical subchannel number can be set toa number in the range of k to N (1≦k≦N) belonging to the localizedlogical subchannel region. Alternatively, the localized logicalsubchannel number can be set to a number in the range of 1 to N−k+1 bynumbering a new number starting from a first subchannel of the localizedlogical subchannel region.

When the BS reports the logical subchannel number to the UE, the UE canfind a resource region allocated to the UE so as to transmit or receivedata by using the logical subchannel number. When a frequency resourceregion allocated to the UE is consecutively allocated to be used duringa specific time period (e.g., single/multiple frame numbers), the BS canreport only the logical subchannel number to the UE. That is, the BS canrepresent an indicator for a downlink burst (or uplink burst) allocatedto the UE only with the logical subchannel number. In comparison with a2-dimensional indicator indicating the resource region allocated to theUE with the frequency domain and the time domain, the use of a1-dimensional indicator indicating the resource region only with thelogical subchannel number can reduce an overhead caused by transmissionof resource allocation information.

Optionally, one frame can be one distributed logical subchannel regionor one localized logical subchannel region of the whole frequency band,or the whole frequency band can be segmented within one frame along atime or frequency domain to constitute the distributed or localizedlogical subchannel. That is, a subchannel configuration methodconsidered in a legacy system can be directly used within one frame. Thelegacy system may be an IEEE 802.16e system or a WiMAX system. However,the present invention is not limited thereto, and thus the legacy systemmay be any conventional system. The proposed subchannel configurationmethod may be used alone or in combination with the subchannelconfiguration method of the legacy system. Since the frame configurationmethod of the legacy system and the proposed frame configuration methodcan be combined to be used, the frame can be configured in a flexiblemanner.

FIG. 7 shows a frame structure according to another embodiment of thepresent invention. The frame is an uplink frame that can indicatefrequency-time physical resource allocation.

Referring to FIG. 7, a physical frame includes a data region and/or aranging or UL control channel region. The data region includes adistributed region and a localized region. The ranging region is used totransmit a ranging preamble of a UE. The ranging or UL control channelregion, the distributed region, and the localized region are separatedin a frequency domain. That is, the ranging or UL control channelregion, the distributed region, and the localized region use a frequencydivision method. The respective regions can use different permutationrules. In addition, some subchannels corresponding to the distributed orlocalized region can be allocated to the ranging or UL control channel.

FIG. 8 shows a logical frame for the physical frame of FIG. 7. Thelogical frame may be an uplink frame. The logical frame is constitutedby performing logical mapping from the physical frame.

Referring to FIG. 8, the logical frame includes an uplink or downlinkburst. A distributed region of the physical frame is mapped to adistributed logical subchannel region. A localized region of thephysical frame is mapped to a localized logical subchannel region.

A ranging or UL control channel can be influenced by a configurationmethod of the UL control channel in a legacy system. A pre-assignedfrequency domain needs to be spanned and transmitted during a pluralityof OFDM symbol durations. Therefore, in a method of allocating resourceswithin a frame, the distributed logical subchannel region and thelocalized logical subchannel region can be configured for afrequency-time resource region except for the ranging or UL controlchannel region. In the logical frame, the logical subchannel numbers canbe determined as described in FIG. 6 above. A BS can transmitinformation regarding the ranging or UL control channel region through acommon control channel of a downlink frame. If the common controlchannel is included in some of frames included in a super-frame, theconfigured logical uplink frame may not include information regardingthe ranging or UL control channel region.

The aforementioned frame structure is for exemplary purposes only, andthus the present invention is not limited thereto. In the physicalframe, locations and sizes of the distributed region, the localizedregion, and the control channel are not fixed but are variable withinsubframes. In the logical frame, locations and sizes of the distributedlogical subchannel and the localized logical subchannel are not fixedbut are variable within subframes. If the frame of FIG. 5 is a downlinkframe and the frame of FIG. 7 is an uplink frame, the uplink frame andthe downlink frame can configure subframes by using not only the TDDscheme but also the FDD scheme.

To allocate frequency-time resources in a flexible manner, there is aneed to reduce an overhead of resource allocation information providedfrom a control channel transmitted in one or more frame units. That is,in order for the BS to report resources allocated to each UE by using anindex of the logical subchannel, there is a need for an effective methodof configuring resource allocation information for the distributedregion and the localized region. In addition, an effective method ofresource allocation is required for the case where different frameconfiguration methods are used within an FDD band.

Hereinafter, a method of flexible resource allocation for configuringthe proposed frame will be described. In the proposed frame, two or morepermutation rules can be considered within one OFDM symbol or one slotor one subframe. For this, a subchannel can be configured by segmentinga physical frequency-time resource region into a distribute region and alocalized region. Accordingly, a downlink or uplink burst is formed byallocating a logical subchannel to a UE.

FIG. 9 is a flowchart showing a method of mapping a physical resource toa logical resource according to an embodiment of the present invention.

Referring to FIG. 9, a physical frequency band is divided into at leastone frequency partition (step S110). The physical frequency bandincludes a plurality of subcarriers. The plurality of subcarriers can berearranged according to a specific permutation and thus can bedistributed over the frequency partition. The frequency partition can beclassified into a distributed region and a localized region. Thedistributed region can be used to obtain a frequency diversity gain. Thelocalized region can be used to obtain a frequency selective gain. Thephysical frequency band can be divided into at least one frequencypartition according to a frequency reuse factor. Frequency reuse isachieved by allocating a physical frequency by segmenting the physicalfrequency with respect to each sector. By segmenting each sector,inter-cell interference can be reduced and data transfer reliability canbe improved.

The frequency partition is mapped into a logical resource unit (stepS120). The logical resource unit denotes a basic unit for allocating alogical resource. In addition, the logical resource unit denotes a basicunit for mapping from a physical resource to a logical resource. Forexample, the logical resource unit may be a distributed logicalsubchannel or a localized logical subchannel. A localized region can bedirectly mapped into the logical resource unit. A distributed region canbe mapped into the logical resource unit by rearranging subcarriersincluded in the distributed region according to a specific permutationrule.

A process of mapping the physical resource to the logical resource canbe performed according to some or all of the following steps. As aresult, uplink and/or downlink resource allocation control informationcan be configured.

<Physical Frequency-Time Resource Allocation>

(1) Application of segmentation supporting frequency reuse (2) Reservedranging or UL control channels (UL resource allocation ONLY) (3)Determination of resource allocation unit (4) Frequency bandseparation—distributed/localized region

<Logical Frequency-Time Resource Allocation>

(5) Distributed/localized sub-channelization using the pre-definedpermutation rules (6) Assignment of logical subchannel indices to mobileterminals (7) Data mapping on the assigned logical subchannels

(1) Application of Segmentation Supporting Frequency Reuse

FIG. 10 shows segmentation supporting frequency reuse according to anembodiment of the present invention. This segmentation is physicalfrequency-time resource segmentation.

Referring to FIG. 10, frequency-time resources can be segmented andallocated within a frame. A physical frequency band can be segmented andallocated for each sector within the frame. By segmenting each sector,inter-cell interference can be reduced and data transfer reliability canbe improved. For example, when using a dedicated control channel, acontrol signal can be transmitted by increasing frequency reuse of aband robust to the inter-cell interference in order to guarantee qualityof service (QoS) and to improve reliability. However, a throughput maybe decreased due to deterioration of spectral efficiency, and additionalcontrol signal transmission may be requested for inter-cell frequencyallocation.

Such segmentation can be analyzed as a method of configuration from aphysical resource to a logical resource, and can be extensively appliedto a method of configuring a subchannel. That is, as in the case ofsegmenting the physical frequency band for each sector, the physicalresource can be divided into at least one frequency partition. In thiscase, a specific permutation rule can be used when the physical resourceis segmented into the frequency partition. For example, the physicalresource can be divided with various sizes in a frequency domain, andthe physical resource divided in the frequency domain can be rearrangedaccording to a permutation. The rearranged physical resource issegmented into a plurality of frequency partitions. Each frequencypartition can be independently divided into a distributed region and/ora localized region. The distributed region and the localized region ofeach frequency partition are mapped to a logical subchannel. The logicalsubchannel can be divided into a distributed logical subchannel regionand a localized logical subchannel region. The distributed region can bemapped to the distributed logical subchannel region. The localizedregion can be mapped to the localized logical subchannel region.

(2) Reserved Ranging or UL Control Channels (UL Resource AllocationONLY)

In case of uplink, a specific frequency band can be pre-assigned to beused for improvement of coverage and improvement of reliability ofcontrol signals and multiplexing capability. In this case, subsequentprocesses are performed on remaining regions other than the pre-assignedfrequency domain for the ranging or control channel in a physicalfrequency-time resource structure allocated by performing segmentationor the like.

(3) Determination of Resource Allocation Unit

FIG. 11 shows a resource allocation unit according to an embodiment ofthe present invention.

Referring to FIG. 11, a physical frequency-time region is configuredthrough segmentation except for a ranging or UL control channel region.The physical frequency-time region needs to be allocated by dividing itinto a distributed region and a localized region. A basic unit fordistributed/localized resource allocation needs to be defined toeffectively indicate resource regions. The basic unit may be a physicalresource unit for allocating physical resources. The basic unit mayinclude a plurality of subcarriers in a frequency domain and at leastone OFDM symbol in a time domain. For example, the basic unit may be aslot or a resource block. In a logical resource, the basic unit may be alogical resource unit for allocating logical resources. In the logicalresource, the basic unit may be a subchannel.

The basic unit may be represented using a 2-dimensional configurationmethod specifying a frequency and a time or a 1-dimensionalconfiguration method specifying a frequency or a time. A 1-dimensionalbasic unit may be represented by specifying a frequency band such as asubchannel index or a subcarrier index or by specifying a time band suchas an OFDM symbol or a slot index. The 1-dimensional basic unit can beeasily applied using a 2-dimensional basic unit. For simplicity, the2-dimensional basic unit will be described hereinafter.

The 2-dimensional basic unit can include one or more consecutivesubcarriers and OFDM symbols in a frequency-time domain. By increasingthe size of the 2-dimensional basic unit, an overhead of resourceallocation information can be decreased but a multi-user gain or afrequency selective scheduling gain through resource allocation may alsobe decreased. Therefore, the basic unit has to be designed byconsidering a radio channel characteristic so as to decrease theoverhead and to obtain effective additional gains. For this, thefrequency domain of the basic unit can be determined within a coherencebandwidth by considering a delay spread resulted from a multi-pathchannel characteristic. In addition, the time domain of the basic unitcan be determined within a coherence time by considering a time-variantchannel characteristic which is taken into account in an environmentwhere a mobile object moves with a high-speed. For example, the basicunit may consist of a maximum of 16 consecutive subcarriers in thefrequency domain and a maximum of 4 consecutive OFDM symbols in the timedomain. In particular, the basic unit of the frequency domain can bedefined variously according to an FFT size. For a small-sized FFT (e.g.,128 FFT size), a basic unit for a frequency domain having a relativelynarrow range can be configured. For a relatively larger-sized FFT (e.g.,2048 FFT size), a basic unit for a frequency domain having a wide rangecan be configured. In addition, a basic unit for a time domain havingone subchannel or a time domain for forming a predetermined number ofsubchannels (where the predetermined number is an integer multiple) canbe configured, and also can be utilized for data region segmentation.

One frame can be segmented into a plurality of 2-dimensional basicunits. A number (i.e., index or indicator) can be numbered to indicatethe segmented basic units. The number is sequentially numbered for thesegmented basic units along the frequency domain, and can be extensivelyapplied along the time domain. This is for exemplary purposes only, andthus the numbering on the basic units may be achieved in variousmanners. Numbering may be sequentially performed first on the timedomain for the segmented basic units and then may be extensively appliedto the frequency domain. Alternatively, random numbering can beperformed on the basic unit according to an arbitrary or predeterminedinterleaving scheme. Accordingly, there may be an advantage in that adiversity effect can be obtained in the time or frequency domain andinfluence of inter-cell interference can be decreased.

(4) Frequency Band Separation—Distributed/Localized Region

Frequency band separation can be achieved using a basic unit.Information on a data region can be transmitted through a controlchannel (or dedicated control channel) transmitted in one or moreframes. A method of dividing the data region and a frame structure of alegacy system can be used in the proposed frame structure.

First, a legacy frame structure using an FCH and a MAP in the legacysystem will be described. When a plurality of permutation zones areallocated and utilized in a frame structure having a shot length, systemefficiency can be improved in comparison with a TDD-based framestructure. Disadvantageously, however, an overhead of controlinformation and a scheduler complexity can be increased. It may beimportant to consider a method capable of supporting FDD whilemaintaining the legacy frame structure in terms of backwardcompatibility with the legacy system. Therefore, it is preferable toextensively apply additional functions while maintaining theconventional method of configuring control information of a frame. Forexample, the control information may be configured using theconventional downlink frame prefix (DLFP) and MAP, and additionalfunctions may be extensively applied. Thus, a frame can be configuredwith a new format while maintaining the legacy frame configurationmethod. As shown in FIG. 3, for one or more OFDM symbols at a startposition of the frame, the FCH and the DL-MAP can be transmitted using apermutation rule applied in the legacy system. The FCH can indicatewhether the conventional legacy frame structure or the proposed framestructure will be used. A mode indicator indicates a legacy mode inwhich the legacy frame structure is applied and a new mode in which theproposed frame structure is applied. The mode indicator can be expressedas follows.

${{Mode}\mspace{14mu}{Indicator}} = \begin{pmatrix}{0,} & {{legacy}\mspace{14mu}{mode}} \\{1,} & {{New}\mspace{14mu}{mode}}\end{pmatrix}$

This is for exemplary purposes only. Thus, the legacy mode may beindicated when the mode indicator is ‘1’, and the new mode may beindicated when the mode indicator is ‘0’. Migration between the legacymode and the new mode can be achieved by adding the mode indicator inthis manner to determine a configuration method of a correspondingframe. 1-bit mode information can be transmitted through the FCH, thecommon control channel, the preamble, etc.

Even if the conventional legacy mode is directly used, configuration ofa plurality of permutation zones during a short frame length may beineffective. In this case, in addition to a permutation rule applied inthe control channel, there is a need to apply one or two zones to thedata region through segmentation. In this case, 2-dimensional resourceallocation information (i.e., an OFDMA symbol offset+a subchanneloffset+the number of subchannels+the number of OFDMA symbols) of afrequency-time domain conventionally used to indicate a downlink burstin the DL-MAP can be transmitted, which may lead to increase in anoverhead of a downlink control signal. If it is assumed that a downlinkburst region is allocated by being separated along a frequency domainwithin a permutation zone, DL-MAP information can be configured onlywith a subchannel offset and a value indicating the number ofsubchannels. In case of uplink, a slot duration used by an uplink burstcan be used for region identification, and each UE can identify itsburst through accumulation of slot durations allocated to other UEs. Inthis case, the uplink burst may be identified with a logical subchannelindex or may be identified with a subchannel offset and a valueindicating the number of subchannels.

Now, allocation of a new data region based on a basic unit will bedescribed. A concept of the permutation zone of the legacy system can beextended to additionally divide a data region so that a distributedresource allocation scheme and a localized resource allocation schemecan be used together in one resource region. In this case, controlinformation indicating whether a conventional or new resource allocationscheme will be used within a frame may be indicated by using an FCH or aDL-/UL-MAP so that configuration is achieved using the conventional ornew resource allocation scheme within the frame.

Information for identifying a distributed data region or a localizedregion within the frame can be transmitted by considering predeterminedbasic unit numbering according to a 1-dimensional division method or a2-dimensional division method.

FIG. 12 shows a method of dividing a data region according to anembodiment of the present invention. This is a 1-dimensional divisionmethod specifying a frequency domain.

Referring to FIG. 12, one subframe can be divided into a distributedregion and a localized region in the frequency domain. The distributedregion and the localized region can be divided from at least onefrequency partition segmented according to a specific permutation rule.For the distributed region and the localized region, the dividedfrequency domain can be used within one frame to decrease an overhead ofresource allocation control information by considering a short subframelength. In control information such as a DL/UL-MAP, division informationof the frequency domain can be reported using 1-dimensional controlinformation specifying the frequency domain.

Division information of the distributed region and the localized regioncan be reported in a bitmap format. For example, a whole frequency bandof a subframe is divided into k bits, so that a frequency band having abit value of ‘1’ indicates a localized region and a frequency bandhaving a bit value of ‘0’ indicates a localized region. Of course, theother way around is also possible. That is, the frequency band having abit value of ‘1’ may indicate the distributed region and the frequencyband having a bit value of ‘0’ may indicate the localized region. Inaddition, the distributed region and the localized region can beindicated using a basic unit number.

FIG. 13 shows a method of dividing a data region according to anotherembodiment of the present invention. This is 2-dimensional divisionmethod specifying a frequency domain and a time domain.

Referring to FIG. 13, when a distributed region and a localized regionare not spanned during the time domain of one subframe, the2-dimensional division method is required in which the frequency domainand the time domain are specified. Control information of the2-dimensional division method may have an increased overhead caused bytransmission of the control information in comparison with controlinformation of the 1-dimensional division method, but can effectivelyuse a frequency-time resource. For this, a resource unit number can beused as control information regarding resource allocation.

Information on one distributed region or localized region within a framecan be reported using a start position (or index) of a basic unit for asegmented data region, the number of time-domain basic units in the timedomain for an allocated data region, and the number of frequency-domainbasic units in the frequency domain. Information on an offset of thefrequency domain and the time domain and a start time point thereof canbe expressed with a frequency-time starting point at which the framestarts, a first frequency or time starting point at which a segmentationregion is applied, etc. A basic unit in association with a positionhaving a greatest offset of the frequency domain and the time domain canbe determined using a resource allocation starting point.

In a case where a subframe is divided into a plurality of data regionswith respect to the distributed region or the localized region, anoverhead caused by control information on resource allocation canincrease. To reduce the overhead of the control information on resourceallocation, only information on the distributed region may betransmitted and the remaining regions may be configured as the localizedregions, or only information on the localized region may be transmittedand the remaining regions may be configured as the distributed regions.In such a case, by transmitting information on both the distributedregion and the localized region, the overhead can be reduced more thanhalf.

In addition, in the allocation of a plurality of data regions, a startposition of the data region can be determined in various manners byusing the basic unit.

FIG. 14 shows a method of determining a start position of a data regionaccording to an embodiment of the present invention.

Referring to FIG. 14, start positions of a plurality of data regions canbe determined in various manners by using a basic unit.

In a first method (i.e., Method 1), a start position of a data regioncan be indicated by information on a frequency-domain basic unit offsetand a time-domain basic unit offset. In this case, a frequency-timereference position for the start position of the basic unit may be afrequency-time domain at which a control channel ends or afrequency-time domain at which each subframe starts.

In a second method (i.e., Method 2), a start position of a data regioncan be indicated by a position (i.e., index or a indicator number) of anactual basic unit. The start position of the data region may bedetermined to be a position of a smallest or largest basic unit in thedata region. Further, 2-dimensional resource allocation information canspecify division of an allocation region by simultaneously transmittingtwo pieces of information on start and end positions of a basic unit ofan allocation region. In comparison with information delivery using thefirst to the third methods mentioned herein, an amount of controlinformation can be reduced most efficiently in the Method 2.

In a third method (i.e., Method 3), for a plurality of data regions, astarting point of a basic unit for a data region first allocated, and aposition of a basic unit at a starting point of another data region canbe indicated with a differential value. The differential value maydenote a difference between basic unit numbers in a frequency domainand/or a time domain.

In a fourth method (i.e., Method 4), if a plurality of data regions havethe same start position in a time domain, a start position of a dataregions can be indicated in a bitmap format. If a distributed region isallocated, it may be effective to start allocation of the data region ata start position of a frame in consideration of a feedback delay so thata multi-user gain or a frequency selective gain can be obtained byutilizing channel information collected through a feedback channel.

<Logical Frequency-Time Resource Allocation>

(5) Distributed/Localized Sub-Channelization Using the Pre-DefinedPermutation Rules

Resource allocation in a physical frequency-time domain can be subjectedto distributed/located sub-channelization using the pre-definedpermutation rules. For physical frequency-time domain allocation, apermutation rule can be applied by separating a distributed/localizedregion allocated using a logical subchannel generation method. Asubchannel can be configured to facilitate sub-channelization of a basicunit, and thus the subchannel can be generated irrespective ofallocation of a data region. However, in case of a distributedsubchannel, a configuration of a plurality of basic units may benecessary in order to obtain a sufficiency frequency diversity gain. Forthis, there is a need to set a condition for configuring at least twobasic units within a unit time by using the number of distributedsubchannels. The unit time is a time corresponding to one basic unit ora basic time unit for the subchannel generation method. When asubchannel is generated for the distributed region or the localizedregion, a logical subchannel index may be numbered individually for thetwo regions or may be sequentially and consecutively numbered.

(6) Assignment of Logical Subchannel Indices to Mobile Terminals

After generating and numbering logical subchannels, logical subchannelindices can be assigned to the mobile terminals. That is, the logicalsubchannel indices are assigned for downlink bursts or uplink burstsallocated to the respective mobile terminals. Control information onlogical subchannel index assignment may be transmitted differentlyaccording to a distributed subchannel region and a localized subchannelregion. In case of the distributed subchannel region, a frequencydiversity and inter-cell interference randomization are considered inthe subchannel itself. Thus, an overhead of the control information canbe reduced by consecutively assigning the subchannel indices to be usedby the respective mobile terminals. For example, information on thedistributed subchannel can be known by reporting an index of a startposition of the distributed subchannel region, the number of subchannelsincluded in the distributed subchannel region, or a last position of aconsecutively allocated distributed subchannel. Information on thelocalized subchannel region can be known by using a bitmap format orinformation of each subchannel index in some cases where inconsecutivelogical subchannels need to be allocated.

(7) Data Mapping on the Assigned Logical Subchannels

Data is mapped to the assigned logical subchannels. In a method ofmapping to-be-transmitted data on the logical subchannel regionallocated to each mobile terminal, time-domain mapping may be firstperformed, followed by frequency-domain mapping. Alternatively, thefrequency-domain mapping may be first performed, followed by thetime-domain mapping. Optionally, data can be mapped according to apre-defined rule, such as, a hopping scheme or an interleaving scheme inwhich mapping is carried out with a specific distance. Data can be1-dimensionally or 2-dimensionally mapped in an allocated region.

FIG. 15 is a block diagram showing constitutional elements of a UE.

Referring to FIG. 15, a UE 50 includes a processor 51, a memory 52, aradio frequency (RF) unit 53, a display unit 54, and a user interfaceunit 55.

Layers of a radio interface protocol are implemented in the processor51. The processor 51 provides the control plane and the user plane. Thefunction of each layer can be implemented in the processor 51. Theprocessor 51 divides a physical band into at least one frequencypartition, and each frequency partition is divided into a localizedregion and a distributed region in a frequency domain. The processor 51maps the at least one frequency partition into at least one logicalresource unit. In this case, the localized region is directly mappedinto the logical resource unit, and the distributed region is mappedinto the logical resource unit by rearranging subcarriers according to apre-defined permutation rule.

The memory 52 is coupled to the processor 51 and stores an operatingsystem, applications, and general files. The display unit 54 displays avariety of information of the UE 50 and may use a well-known elementsuch as a liquid crystal display (LCD), an organic light emitting diode(OLED), etc. The user interface unit 55 can be configured with acombination of well-known user interfaces such as a keypad, a touchscreen, etc. The RF unit 53 is coupled to the processor 51 and transmitsand/or receives radio signals.

Every function as described above can be performed by a processor suchas a microprocessor based on software coded to perform such function, aprogram code, etc., a controller, a micro-controller, an ASIC(Application Specific Integrated Circuit), or the like. Planning,developing and implementing such codes may be obvious for the skilledperson in the art based on the description of the present invention.

Although the embodiments of the present invention have been disclosedfor illustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope of the invention. Accordingly, the embodimentsof the present invention are not limited to the above-describedembodiments but are defined by the claims which follow, along with theirfull scope of equivalents.

What is claimed is:
 1. A method of transmitting data by a transmitter,the method comprising: interleaving data; mapping the interleaved datainto a frame including a plurality of OFDM (Orthogonal FrequencyDivision Multiplexing) symbols in a time dimension and a plurality ofsubcarriers in a frequency dimension; and transmitting the frame whichincludes an information region and a data region, wherein the dataregion is divided into a first data region including a first type of oneor more resource units and a second data region including a second typeof one or more resource units, wherein data in the first type of one ormore resource units are mapped to the first data region by a firstmapping scheme and data in the second type of one or more resource unitsare mapped to the second data region by a second mapping scheme otherthan the first mapping scheme, and wherein the information regionincludes information to identify a type of each of the resource units.2. The method of claim 1, wherein the information region furtherincludes information to indicate a start position of at least one of theresource units.
 3. The method of claim 1, wherein the information regionfurther includes information related to a number of the resource unitswithin the frame.
 4. The method of claim 1, wherein the informationregion is divided into a first information part and a second informationpart, wherein the first information part includes at least one ofinformation to indicate a size of the second information part orinformation to indicate a coding scheme of the second information part,and wherein the second information part includes the information toidentify the type of each of the resource units.
 5. The method of claim1, wherein the first mapping scheme allocates the data in the first typeof one or more resource units to subcarriers of the first data region inthe frequency dimension by a consecutive manner and the second mappingscheme allocates the data in the second type of one or more resourceunits to subcarriers of the second data region in the frequencydimension by a distributed manner.
 6. An apparatus that transmits data,the apparatus comprising: a processor that interleaves data and maps theinterleaved data into a frame including a plurality of OFDM symbols in atime dimension and a plurality of subcarriers in a frequency dimension;and a transmitting unit that transmits the frame which includes aninformation region and a data region, wherein the data region is dividedinto a first data region including a first type of one or more resourceunits and a second data region including a second type of one or moreresource units, wherein data in the first type of one or more resourceunits are mapped to the first data region by a first mapping scheme anddata in the second type of one or more resource units are mapped to thesecond data region by a second mapping scheme other than the firstmapping scheme, and wherein the information region includes informationto identify a type of each of the resource units.
 7. The apparatus ofclaim 6, wherein the information region further includes information toindicate a start position of at least one of the resource units.
 8. Theapparatus of claim 6, wherein the information region further includesinformation related to a number of the resource units within the frame.9. The apparatus of claim 6, wherein the information region is dividedinto a first information part and a second information part, wherein thefirst information part includes at least one of information to indicatea size of the second information part or information to indicate acoding scheme of the second information part, and wherein the secondinformation part includes the information to identify the type of eachof the resource units.
 10. The apparatus of claim 6, wherein the firstmapping scheme allocates the data in the first type of one or moreresource units to subcarriers of the first data region in the frequencydimension by a consecutive manner and the second mapping schemeallocates the data in the second type of one or more resource units tosubcarriers of the second data region in the frequency dimension by adistributed manner.